Besides hard and soft corals, there are other spectacular and strange relatives of corals and sea anemones on our reefs and shores! Here's a glimpse at some of them.
The flamboyant peacock anemone (Order Ceriantharia) is a large, solitary polyp that burrows in soft ground and lives permanently in a tube. So it is also sometimes called the Tube anemone or the Burrowing anemone.The Peacock anemone has two types of tentacles. An outer ring of long graceful tentacles that gather food from the water. And an inner ring of shorter tentacles that tuck food into the mouth in the centre.
Peacock anemones come in many different colours and patterns, hence their common name.
Corallimorphs (Order Corallimorphoria) sometimes form colourful carpets on rubbly areas. They are solitary polyps, although they are often found in groups and may sometimes grow over large areas of coral rubble.Corallimorphs are distinguished by an upturned mouth in the centre of the oral disk. Most other sea anemones and corals have inward turning mouths.
Corallimorphs also lack long tentacles and just have bumps or ridges instead.
Hydroids (Order Hydrozoa) can be common on our rubbly areas, growing even on jetty pilings. They are colonial animals made up of tiny polyps. The colony often takes on feathery, branching plant-like forms.Some colourful nudibranchs like this purple-and-orange Cuthona sibogae feed on hydroids.The polyps of the pale hydroid packs a powerful sting that can cause severe pain and irritation in careless divers and shore explorers. This is why it's important to avoid touching anything on the shores.
Jellyfish are not fishes! They are related to sea anemones and indeed, look like upside down sea anemones. Jellyfish are more notable for the features that they lack: no head, no organs, no bones.The animal moves by contracting its bell-shaped body. Tentacles may trail under the body, though some species do not have long and obvious tentacles.
Jellyfish of various kinds are sometimes seasonally common in our waters. And when in 'bloom' can wash ashore in large numbers. Jellyfish can sting and some, very painfully. So don't touch jellyfish, even if they are stranded on the beach.
The sea pen (Order Pennatulacea) is more commonly seen on our Nothern shores among seagrasses and in silty soft area. Some sea pens resemble a feathery stalk: sea pens are so named because they resemble feather quill pens.
A sea pen is a colony of different types of polyps. The central stalk is one individual animal that supports the whole colony. The bottom half anchors the colony and retracts the whole colony into the ground at low tide. The upper half of the central stalk sticks out of the surface. Here, other kinds of polyps emerge with tentacles that filter feed at high tide.In some sea pens, a pair of pretty spotted porcelain crabs may be found sheltering among the 'fronds'.
Some sea pens look like flowery sausages. Yet others look more like sea pencils or sticks with short leafy flaps.
Zoanthid or Colonial Anemones
Zoanthids (Order Zoanthidea) are commonly seen on rubbly areas. They look like tiny sea anemones.
But while sea anemones are solitary polyps, most zoanthids live in colonies like corals do. So they are sometimes called colonial anemones. But zoanthids don't produce a hard skeleton like the hard coral colonies. Instead, their skin is leathery and composed partly of chitin.
When exposed at low tide they may retract their tentacles and look like strange blobs of jelly. Some zoanthids look like rubbery mats when the polyp tentacles are retracted.
We certainly have all kinds of strange-looking marine life on our reefs and shores! Do take a closer look the next time you are on the shore.
Links to more
Photos on wildsingapore flickr